All my controllers are drifting right now or when I'm playing any game that involves pressing in L3 to run, can barely run for 2 seconds before stopping. Also, I can't even walk backwards when I play Cawadoody. Sucks when someone throws a nade and you have to do a 180 just to run away.
You can, it's not that hard. You'll need a special type of screwdriver to get it open (like a Torx T something). You could also order replacement sticks off of eBay for pretty cheap (like just a few dollars). But that might not be the problem. It could be the metal stick that is soldered to the board that is under the stick. If that is the case, then you're pretty much doomed to a drifting stick for the rest of the controllers life. I'd try replacing the sticks first though to see if that is the problem. You can also wipe down the crevices and get the dirt out while you have it apart.